1. Field of the Invention
The present invention relates to a radio base station of a mobile communication system that performs packet communication and to a method of setting scheduler algorithms in the radio base station.
2. Description of the Related Art
The demand for high-speed data communication in mobile communication systems has been growing in recent years. In regard to these systems, rapid advances have been made in the standardization and development of HSDPA (High-Speed Downlink Packet Access) technology to realize higher downlink packet communication speeds in W-CDMA, which is a third-generation mobile communication system.
In HSDPA, a radio base station performs scheduling that controls the frequency of transmission of packet data to a plurality of mobile stations in accordance with the radio characteristics of each mobile station in order to improve throughput by means of a user multiplexing effect. Representative scheduler algorithms include the MAX-C/I (Maximum Carrier Interference Ratio) form and the PF (Proportional Fairness) form.
The MAX-C/I form is an algorithm by which scheduling is carried out such that packet data that await transmission are preferentially transmitted to the mobile station having the best radio characteristics from among stations that are the transmission destinations. This method has the capability of increasing the throughput characteristic, but the frequency of transmission of packet data to mobile stations having poor radio characteristics is low.
The PF form is an algorithm used for the transmission of packet data, that await transmission, equally to all mobile stations that the destinations of this packet data. As a result, a certain proportion of transmission opportunities are equally assigned to mobile stations having poor radio characteristics.
The two forms described above are statically set and do not allow dynamic alteration during operation. A system therefore will have a fixed characteristic according to which, once the MAX-C/I form has been set to prioritize improved throughput characteristics, it (the system) will not carry out the transmission of packet data equally to all mobile stations that are the transmission destinations, or it will suffer from degraded throughput characteristics once the PF form has been set to prioritize transmissions equally to all mobile stations.
The present applicants have devised and submitted an application for a method of dynamic operation in which two schedulers, the MAX-C/I form and the PF form, are provided in a radio base station, and in which the required service quality, which is the band required to transmit the packet data, is calculated when there are packet data that are to be transmitted to mobile stations. Scheduling is then carried out using the scheduler algorithm of the PF form when, based on the result of comparing the calculated value and the demanded service quality, i.e., the demanded band, the required service quality is greater than the demanded service quality; and scheduling is carried out using the scheduler algorithm of the MAX-C/I form when the required service quality is less than the demanded service quality. The required service quality is the band quality necessitated by the mobile system. The demanded service quality is the band quality required by the user.
A method for, in accordance with the load on the CPUs of communication devices, changing the encryption algorithms of communication data between communication devices and communication terminals that are connected by way of a network is disclosed in, for example, JP-A-2004-254286.
However, the above-described method of setting scheduler algorithms that employs required service quality and demanded service quality has the drawback that the required service quality must constantly be calculated. In addition, the method disclosed in the above-described patent document has the drawback that the rate of use of CPUs must be measured.